Generally, stone bed is a kind of bed which has been developed for those who are accustomed in the under-floor heating system. As shown in FIG. 1, this stone bed is constituted as follows.
That is, a supporting frame unit 10 forms the basic frame which is necessary for forming the entire bed, and on the upper face of the supporting frame unit 10, there are mounted auxiliary elements such as a fixed plate 20, an insulating plate 30, a supporting plate 40 and a stone plate 50, thereby forming a stacked mattress 60.
However, in this conventional stone bed, the supporting frame unit is a necessary basic constituent upon which the mattress is settled. As a result, the manufacturing cost increases due to the presence of the supporting frame unit, thereby aggravating the economy.
Further, if the stone bed is to be moved to change its position, the moving is very troublesome due to the large bulk and weight of the stone bed, and therefore, the handling problem becomes serious.
Meanwhile, in the above described conventional stone bed, the mattress elements such as the fixed plate, the electro-heating plate, the supporting plate and the stone plate are simply stacked without any securing means but resorting only to their gravities. Accordingly, during the handling of the stone bed, if the bed is set upside down or set vertically, then the mattress elements including the fixed plate, the electro-heating plate, the supporting plate and the stone plate depart from the supporting frame unit, with the result that the mattress elements are subjected to damages.